This case-control study will determine the risk that males will develop testicular cancer after exposure to diethylstilbestrol in utero. The case population will be drawn from the list of primary testicular cancers reported in Connecticut residents between 1945 and 1977. The cases studied will be those who were also born in Connecticut between 1945 and 1972. Two control groups, one drawn from birth certificates and the other from hospital populations, will be selected. Drug histories will be obtained from hospital records and from prenatal records of mothers. Other factors to be evaluated include exposure to other exogenous estrogens in utero, cryptorchidism, and hypoplastic testes.